Vulcanization of rubber



Patented July 28, 1936 VULQANIZATION OF RUBBER Robert L. Sibley, Nitro, W. Va., assignor, by mesne assignments, to Monsanto Chemical Company, Wilmington, DeL, a. corporation of Delaware No Drawing. Application August 30, 1930,

Serial No. 479,100

Claims. (CI. 1853) The present invention relates to the vulcanization of rubber by an improved process wherein:

the products obtained by reacting a mercaptoaryl-thiazole, or an alkali salt thereof and the like with an aromatic acid halide are employed as vulcanization accelerators. among rubber chemists that mercapto-arylthiazoles constituteua group of vulcanization accelerators. ing a mercapto-aryl-thiazole, such for example, as the sodium salt of mercapto-benzo-thiazole with an aromatic acid halide, such for example as phthalyl chloride, benzoyl chloride and the like, there is formed an important class of compounds which may be employed alone as a vulcanization accelerator but preferably are employed in conjunction with a basic organic nitrogen containing vulcanization accelerator as an activator thereof, forming thereby a mixed accelerator possessing characteristic and highly desirable properties. I

The invention will be fully understood from the following description and examples of preferred means of practicing the process claimed.

A rubber stock was compounded in the usual manner comprising 100 parts of pale crepe rubber,

5 parts zinc oxide, 3 parts of sulfur, and 1.0 part riods of time under temperatures given by different steam pressures, the following tensile data were obtained.

Table I Modulus of elasticity in lbsJinfiatelongations Tensile Elonga- Cure Pressure at break tion at mins. lbs. steam 1n 7 break,

300% 500% 700% lbs./1n. percent It is well known 20 40 100 191 476 1455 920 30 40 147 244 629 1930 910 40 163 302 879 2050 870 It has now been found that by react- 146 292 From the above results it is evident that a reaction product of an aromatic acid halide for example phthalyl chloride and a mercapto-arylthiazole, such for example as mercapto-benzothiazole possesses vulcanization accelerating properties. These accelerating properties are substantially increased when the preferred class of accelerators are activated by and employed in conjunction with a basic organic nitrogen containing vulcanization accelerator.

To show the improved action of this preferred class of accelerating compounds when employed in conjunction with a basic organic nitrogen containing accelerator as an activator thereof, a rubber stock was compounded in the usual manner comprising parts of pale crepe rubber, 5 25 parts of zinc oxide, 3 parts of sulfur, 1 part of stearic acid, 0.4 part of the reaction product of phthalyl chloride and the sodium salt of mercapto-benzo-thiazole, designated as accelerator A in the following table, and 0.6 part of a basic organic nitrogen containing accelerator, as illustrated by those set forth in the table.

On testing strips of the above stock, vulcanized by heating in a press for different periods of time at different steam pressures, the following tensile data were obtained.

Table II Modulus of P lbelasti citty iln ress. in. a e on- Tensile at Elon ation Accelerating mixture fig? gamons break in at bgeak, Swain lbs/in. percent 500 per- 700 percent cent Accelerator A 10 40 843 3480 4235 Diphenyl-guanidine 760 Accelerator A 10 40 858 3650 4245 4 Diortho tolyl guanidine.. 7 0 Accelerator A 10 40 560 2325 3480 Hexamethylene tetramine 775 Accelerator A 10 4 Thiocar 0 180 561 1990 935 Accelerator A" Para phenylene diamine Accelerator A" Anhydro formaldehyde aniline Table II--Cont1nued Modulus of 5 P lbelzlrsti itg iln 5 {'85- S. 111. 3 8 011- I r Tenslle at Elongatlon Accelerating mixture jg? gatmn breal; 11 1 at break,

steam 1bs./1n. percent 500 per- 700 per- 7 cent cent Accelerator "A 1.

A ,20 1215 4475 4625 715 Diphenyl-guanidine Accelerator A 1 I 20 1333 4705 595 Diortho tolyl guanidine 1. 15 Accelerator A 15 '20 40 .385 3525 3920 r 740 Hexamethylene tetraminefln'. r Accelerator A 40 297 985 2055 880 Thiocarhanilid r V V Accelerator A T 1 V V r 20 40 463 1750 3235 835 20 20 Para phenylene diamine 7 1 Accelerator A -1 1 20' 40 434 2000 73560 820 Anhydro formaldehyde aniline 1 V V Accelerator A" a 30' 40 1350 4400 680 Dlphenyl-guanidine Accelerator A- 3 25 I. V I 1525 4330 675 Drortho tolyl guanidine... V Accelerator A 1 L 4 30 40 953, 3790 4305 745 Hexamethylene tetramineua Accelerator "A" Y r 30 40 359' 1215 2800 s45 30 1 Thiooarhanilifl 5 r a V 30 Accelerator "A 1 v L 30 537 2140 3505 835 Para phenylene diamine 1-. Accelerator A- r 5 a 30 666 2680 3305 705 t 'Anhvdro formaldehyde aniline 3 5 Accelerator A- 1 45 40 1313 4395 680- Di'phenyl-guanidine Accelerator A-.. r Y r A 40 1495 4450 575 Diortho tolyl 'guanidine Accelerator A" V 5 1 45 40 983 3895 $4455 740 40 Hexamethylene tetrami'ne V a 40 Accelerator A" A 45 "40 405 1365 3145 850 Thiocarhanilifl I Accelerator A Z r 45' 40 507 2235 3580 780 Para phenylene dialmne 4 5 Accelerator A 45 45 40 755 3035 4050 755 Anhydro formaldehyde ani1ine v Accelerator A" V r I 1 00 40 1153 4365- 4365 700' Diphenyl-mm'nirliria 7 Accelerator A r I i i r e0 40 1370. 4530 575 ,Diortho tolyl guanidine 50 Accelerator A v 60 40 925 3740 4120 730 Hexamethylene tetramine "1-1 Accelerator A" 60 40 417 1393 3160 545 Thiomrhanilid 5 :i- Accelerator A a a 2 50- 4o 7 638 2450 3530 775 Para phenylene diamine Accelerator A I '7 a 40 745 3020 a 4100 755 Anhydro formaldehyde aniline .1

From the data set forth m Table II,;1t 1s appar- As a further example of the use of the preferred cut that the preferred class of acce1erat1ng,'com-, ,class of compounds, Inf-31830131011 product of subpounds are very deslrabl-e accelerators, part1custantrally equl-molecular proportwns of benzoyl larly when actlvatcd by a 'baslc orgamc mtrogen chlonde and mercapto-benzo-thrazole was incorcontaming compound Furthermore, the1r 115618" 'porated m the well known manner 1n a rubber especlally advantageous 1n that stocks 1n wh1ch stock compnsmg a they are mcorporated p1l01 to :the vulcamza'tmn V I Parts thereof mamtaln to'a large'extent thelr origmal Pale crepe rubber r V 100 tensrle and modulus characterlstlcs on over our f zinc Oxide, ing. Moreover, although the mlxture 1s effeetlve sulfur "ff f 3 70 I g and a W when tempera -The-react1on product f benzoyl chlonde and tures, 1t 1s not so fast 111 actlon as to produce mercaptmbenzmthiazole 1 prevulcanlzatlon or scorchlng of the stock duri I v v f 'T"' 2 mg the m1ll1ng, calendermg or other handlmg The above stock onvulcamzing by heating in .operatmns. 76,

""a press'for di'ficrent perio s of time at the temperature given by 40 pounds of steam pressure. per square inch, was found to possess the modulus and tensile-characteristics set forth in Table III.

Table III Modulus of elasticity I in lbs/in. at elonga- Tensile Cure Pressure mus at break tion at mine. lbs. steam in break,

. lbs/in! percent 300% 500% 700% I 10 40 as 134. 3 24 1510 900 20 40 110 220 590 2075 920 .30 40 127 243 i 694 w 2500 908 60 4:0 151 302 805 2440 868 40 147 287 803 2470 903 Parts Pale crepe rubber Zinc oxide, 5 Sulfur 3 The reaction product of benzoyl-chloride V and. mercapto-benzo thiazole 0.4 Diphenyl guanidine 0.6

After vulcanizing the above described stock'by heating in a'press for different periods of time at the temperature given by 40 pounds of steam pressure per square inch the modulus and tensile data set forth in Table IV were obtained.

"From the data set forth inTable IV it is ap-' parent that the preferrednew class of rubber vulcaniz'ation accelerators possess particularly desirable accelerating properties, when employed in conjunction with a basic organic nitrogen containing vulcanization accelerator as' an activator thereof, thus forming a mixed accelerator.

As a. further example showing the use of the preferred class of accelerators at the lower steam pressures, the following stock was compounded.

Parts Pale creperubber 100 Sulfur l 12 Zinc oxide ......;,,..=a 5 1 Whiting"- 30 Lithopone 20 Palm oil i z The reactionproduct of phthalyl chloride and mercapto-benzo thiazolea 0.66 Diphenyl guanidine 0.22

The above stock after curing and testing was found to possess the following modulus and tensile characteristics.

Table V Modulus of elasticity in Cum lbs/1n. at elougatlons Tensile Ultimate time Lbs. steam ofat break elongapressure in tion, per

lbs/in. cent 300% 500% 700% The preferred class of materials also show desirable accelerating properties at low steam pressures when incorporated in a gum stock. Thus a rubberstock was compounded in the usual manner comprising.

. Parts Pale crepe rubber 100 Zinc oxide 8 Sulfur 2 The reaction product of phthalyl chloride and mercapto-benzo-thiazole 0.6 Diphenyl guanidine 0.4

The rubber stock thus formed was vulcanized and on testing the cured rubber product was found to possess the following modulus and tensile characteristics.

Table VI Modulus of elasticity in Cure lbs/1n. at elongations T fl Ultimate time Lbs. steam 0 at break elongamins' pressure in tion. per

1 lbs/in. cent Other -mer'capto-aryl-thiazoles than mercaptobenz'o-thiazolemay be reacted with aromatic acid chlorides and employed as accelerators of the vulcanization process. Thus mercapto-tolylthiazole, mercapto-naphtho-thiazole; substituted benzo-thiazoles, such as chlor-mercapto-benzothiazole, amino mercapto-benzo-thiazole and the like may be reacted with phthalyl chloride, benzoyl'chloride and analogous compounds of other aryl acid halides and the product so formed employed as an accelerator, preferably with but, if. desired, without the addition of a basic organic nitrogen containing vulcanization accelerator as an activator thereof.

What is claimed is: V

1. The process of V producing vulcanized rubberwhich comprises heating rubber and sulfur in the presence of a vulcanization accelerator containing a reaction product of an aromatic acid halide and a mercapto-aryl-thiazole as a constituent thereof. V v

2. The process of producing vulcanized rubber which comprises heating rubber and sulfur in the presence of a vulcanization accelerator containing a reaction product of an aromatic acid chloride and a mercapto-aryl-thiazole as a con stituent thereof.

- 3. The process of producing vulcanized rubber which comprises heating-rubberand sulfur in the a mercapto-aryl-thiazole iaS Q. constituent there-' presence of a vulcanization accelerator containing a reaction product of an aromatic acid chloride and a mercapto-benzoethiazole as a constituent thereof.

' 4. The proce'ssof producing vulcaniz i ng rub ride and the sodium salt of mercapto-benzo-thF azole as a constituent thereof. V p 7 v 6. The process of producing vulcanized rubber which comprises heating rubber and sulfur in the presence of a :mixture of vulcanization. ac celerators said acceleratorscomprisinga reaction product of an aromatic acid chloride and a mercapto-aryl-thiazole, and' a basic organic nitrogen containing accelerating compound.

7. The process of producing vulcanized rub-- her which comprises heating rubber and sulfur in the presence of a mixture of vulcanization ac celerators said accelerators comprising a reaction product of an aromatic acid chloride and amercapto-benzo-thiazole, v and a .basic 1 organic nitrogen containing accelerating compound.

8. The process of producing vulcanized rubber which comprises heating rubber and sulfur in the presence of a mixture of, vulcanization accelerators said accelerators comprising a reaction product of an aromatic acid chloride-and a mercapto-benzo-thiazole, and a secondary amine accelerating compound.

9.,The process of producing vulcanized rubber which comprisesjheating rubber'and sulfur in the presence of a mixture'of vulcanization accelerators said accelerators comprising a reaction product of an aromatic acid chloride and a mercapto-benzo-thiazole, and an'aryl substituted secondary amine accelerating compound.

'10. The process of producing vulcanized rubher which comprises heating rubber and sulfur-in the presence of a mixture of vulcanization acc'el-r erators said accelerators "comprising a reaction product of an aromaticacid chloride and a me'rec apto-benzo-thiazole, and an aryl substituted guanidine.

11. The process of producing vulcanized rubber which com rises heating rubber and sulfur in the presence of a mixture of vulcanization accelerators said accelerators "comprising'a re action ,product of an aromaticacid' chloride and a mercapto benzo thiazole and diphenyl 'guanidine.

v 12. The processof producing"vulcanizedgrub ber which comprises heating'rubber "and sulfurin the presence of a a. mixture 'of vulcaniza'tlon accelerators said accelerators comprising-a reaction product of phthalyl "chloride and the diphenyl 'guanidine.

13. The vulcanized rubber product prepared 7 by heating rubber and sulfur in the presence of a vulcanization acceleratorcontaininga reaction 7 product of an aromatic-acid halide and a met capto-aryl-thiazole asa -constituent thereof-if 14. The vulcanized rubber product prepared by heating rubber and sulfurin the presence of a vulcanization accelerator containing 'a freac .tion product of-a'n aromatic acid-chloride -and heating-rubber and sulfur in 'the presencej'of a action product of an aromaticacid halid and i taining a single'benzene nucleus and a mercaptoe of a V V n A g '15. The vulcanized rubber product prepared" by heating rubber and sulfur in the presence of a vulcanization accelerator containing a re-" 7 action product of an aromatic acid chloride and a mercapto-benzo-thiazol'e as a constituent thereof. Q P p p :16. The vulcanized rubber product prepared :by heating rubber and sulfur in. the presence of a vulcanizationaccelerator containing a reaction product of phthalyl chloride and a mercaptobenzo-thiazole as-a constituent thereof.

:17. The vulcanized rubber product preparedb heating rubber and sulfur in the presence o'f'a 15 I vulcanization accelerator containing a reaction product of phthal-yl chloride and the sodiumsalt of mercaptobenzo-thiazole as 'a constituent e eif' p v .18. The vulcanized rubber product preparedby 20 heating rubber and sulfur in the presence of a mixture'o'f vulcanization accelerators, said a e- V celerators comprising a reaction productof an" aromatic acid chloride and a mercaptmaryI- thiazole, and ajbasic organic nitrogen containin accelerating compound. V

. 19.: The vulcanized .rubber product prepared by. heating'rubber and sulfur in thepresenceof a' mixture of vulcanization acceleratorsisaid accelerators comprising a reaction product of an 30' aromatic acid chloride, and -a;mercapto-benzo-j; thiazole and a basic organic nitrogen containingaccelerating compound 1 7 Y,

20. The vulcanized rubber product prepared by mixture-of vulcanization accelerators, said-a'ccelerators comprising a reaction product of [an aromatic acid'chloride and-a mercapto benzo-thi azole. and a secondary amine accelerating compound. fl v Q 1 d "21. The'vu'lcanized'rubber product prepared by heating rubber andisulfur in the presence of a mixture of vulcanizationaccelerators, said accelerators comprising a reaction product ofan aror. matic acid chloride and a mercapto-benzo-thiazole, and an aryl substituted secondary amine r 24. The vulcanized rubber productprepa ed 36 heating rubber and sulfur in the presence of a; mixture of vulcanization accelerators-said accelerators com-prising a reacti'on product of. phthalyl chloride-and the. sodium salt of mercapto -benzo thiazole and diphenyl guanidine. j 25. A composition'of matter comprising a remercapto-aryl-th-iazole. I

26. A composition of matter comprising a re a mercapto benzo-thiazole. r

27. A composition :of matter comprising are-1 action product of an aromatic acid chloride-conaction productof an aromatic acid chloride and j f benzo-thiazole. V

28. A composition of matter comprising a reaction product of phthalyl chloride and a mercapto-benzo-thiazole.

29. A composition of matter comprising a reaction product of phthalyl chloride and the sodium salt of mercapto-benzo-thiazole.

30. A method of treating rubber which comprises adding to the rubber, prior to vulcanization, a compound obtainable by condensing mercaptobenzothiazole with benzoyl chloride in the presence of a dilute caustic soda solution, and then vulcanizing.

31. A method of treating rubber which comprises adding to the rubber, prior to vulcanization, a diarylguanidine accelerator and a compound having the following probable formula:

in which R is an aromatic nucleus attached by two of its adjacent positions and Y is an aromatic nucleus, and then vulcanizing.

32. A method of treating rubber which comprises adding to the rubber, prior to vulcanization,

a compound obtainable by condensing an aryl mercapto thiazole with an aromatic acyl halide and then vulcanizing.

33. A method of accelerating the vulcanization of rubber which comprises vulcanizing in the presence of a compound having the formula 34. A compound possessing the formula if R CSCY,

ROBERT L. SIBLEY. 

